docs: def parse_ecdh(line):
      """Parse ECDH request and return remote public key."""
      prefix, line = line.split(b' ', 1)
      assert prefix == b'D'
      exp, leftover = keyring.parse(keyring.unescape(line))
      log.debug('ECDH s-exp: %r', exp)
      assert not leftover
      label, exp = exp
      assert label == b'enc-val'
      assert exp[0] == b'ecdh'
      items = exp[1:]
      log.debug('ECDH parameters: %r', items)
      return dict(items)[b'e']